Camera shutter



M y 17, 1949. A. w. CAMPBELL CAMERA SHUTTER Filed Feb. 8, 1946 'Co in Vase/9,12 a d Graph/is Patented May 17, 1949 2,470,189 "GEM-ERA SHUTTER Arthur W. aGamploell, Wheaten,

the United Stat es of America; asarepresentedrby the Secretary of War mammals February 8, IMBJSeri aYNo;646,454

10 'Claims. 1

This invention relates to a shutter-mechanism particularly adapted for use with cameras for (taking photographs of detonating explosivesand ;the like.

The principal object L of the present invention :iS theaprovision of ash-utter mechanism having .detonatingmeans associated therewith for comrpletelyzand unitorm-lyi eliminating light from-the .camera :lens in timed relation to the detonation -.of .a light source during the photographing 'of the blast-effect hf adetonating explosives and the like.

A further object is to provideashutter Lmecha- .Qnism consisting of detonating media and a transparent window associated with "a camera lens efor efiectively sealing light rfrom the -lensim- ...mediately after a photograph of detonating explosiveon shell is made.

Still-another obiectds the provisionbfa relavtively simple and inexpensive method and "apgparatusf or effectively sealing light .fro'm a-camer'a lens: after a photograph' of detonatingexplosives ismade.

These and other i objects and advantages-will be '2 apparent by reference -.to the accompanying drawings wherein:

:Figure. 1 is a front-elevation :of the invention illustrating -its position -.on :the inside-wall of a dark bomb-proof testing chamber;

Figure 2 is a a --section Figure 1;

:Figure 3 :is an enlarged 'detail section takeh along-line 4a-3- of Figure 1; and

:Fi-gures 4 and 5illustratetheprogressive stages .of coating after detonation of the fuses.

Referring more particularly to the drawings, wherein similarreferenee characters reier to like parts throughout the several viewsg numeral l designates generally a suitable bellows-type -=.camera,-only*a portion of which is shown. :The camera is adapted tc be'positioned so that the lens 2 thereof is arranged within a suitable .aperture;3-formed in a sidewall A of a dark, bomb-proof, blast explosive testing ichamber. II-he inner end of taken-alongline -2'--2 of the aperture 3 is enlarged; as

at 5, to form a seat within which is suitably :mounted-arel-ativelyrthick; square-shaped, bulletproof protective window 1 of some suitable ltransparent material such as glass. The camera i-s preferably located in a llight-tight r chamber, mot shown; outside-the testing chamber sothat iphotograph is made through the window as' hereinafter described.

.A .frame consisting *of two :spaced, parallel, metal angle bars 8-:is-:suitabl-y attached to-the prima L2, inner-v face 6 of the ch'a berwall '4 by screwswor :the like 5). TWdparal-IeI; spaced, flexibleiabric cord :detonating fuses -l0 -and ll extend through apertures 1 2 "in the angle bars 8 adjacent the ends thereof :so that-they are spaced slightly-fromthe surfaceoffithe glass. The angie bars S of the-frame; aretilted slightly, relative to the -vertical-=axis of the window'fl, as show h in Figures 1, 4 and-'5; so that the fuses a 4 0 and Ai fare arranged and extend angularlyacross the window just above and below the field of view' o f the camera. The fuses are tubular in torml-and containa filler of some suitable high-explosive,"

' such aspentaerythritetetranitrate generally'desig- -n'ated as "PETN. That portion -of the fuses extending between the angle bars- 8 is coated with a mixture of Vaseline and graphite Y I 4 f or a pur- 513086 presently described.

in making flash photographs of deton'ati-ng shells and explosives by the usual shadow tech-'- nioluey-it:has been found that "either the-light intensity or the lens opening must be increased to obtain satisfactory photographs The a increase in the light intensity necessitates the use oftan objectionably large :q'uantity of ex losive in the flashlightpif the intensity "of the light were to be increased wi-thout increasing its duration -time. On the other hand, the 'incr'eazse in the =opening 0f the lens results in the foggingiii -th'efi-lmby luminouspost-detonation phenomena. it has thus been discov'ered that if' the shutter could be made to'operate'quiok1y' enough after the photograph was made, the lens could be opened as wide as desired; "Such ShUttGTEHQS been designed byarranging the prima cord fuse's M d and-ll 'inthe rranfe and mounting tnesame -on the face==of the-window 1 above 'and below the :field of view 'of the camera.

The prime *co1d= fusesare Of-Suc'h'length that they are connected to a cornmon firing-device, such as an electric 'de'tonator, not -shown,=bu't suitabl-y located' at aipoint outside the testing ohamb'er, to "which the" explosive or shell :bfein'g tested in the chamber and the explosive fiash bulb located within thechamber' are also "connected by lengths orprima cord. Neither "the explosive being-"tested or the hash bulb are shown herein andiorm nolpa-rt of theapresent invention. How'- everg-it is to be understood that the-explosive bedng tested is" arranged "within the testing chamber intermediate the flash bulb and the shutter. Thusg" the :vpr-ima coid ius'es H) and H are "sd'm'e "what :longen than the prima cord' extending to :the explosive but slightlyshorter than the c'drd to the fielsh hulb so that therdetonationt nfiithe the fuses will fuses l0 and II will be effected several microseconds after the explosive and at a predetermined point between the respective detonations of the explosive being tested and the flash bulb. By virtue of this arrangement, the products of detonation of the fuses I 0 and II, including Vaseline and graphite, cover the window 7 with a layer or film l5 of soot and carbon and effectively close the window to light.

As the frame holding the fuses is tilted and the detonation along each of the fuses I0 and II is initiated from different directions, that is, in the direction of the arrows in Figure 1, the wave of detonation products emanating from each of be substantially parallel, as illustrated in Figure Land will meet adjacent a central portion of the protective window, as shown in Figure 5, thereby forming a film l5 over the surface of the window and insuring an even and complete cutting off of the light from the camera 1 In other words, as the force of detonation progressively decreases as the fuse it will be apparent that the rate of the Vaseline and graphite coatlens. of each fuse is detonated, of combustion ing on the respective fuses will correspondingly decrease. Thus, by tilting the fuses and initiating the detonation thereof in different directions, the products of combustion from the fuses will build up and flow in the form of a film towards each other, in the direction of the arrows in Figure 4. .1 7

It is to be understood that the detonation of the prima cord fuses l0 and I I will be simultane ous with the detonation of the prima cord extending to the explosive flash bulb and the explosive being tested. However, the sequence of time of the detonation of the flash bulb, the explosive being tested and the fuses l0 and II is regulated by the length of prima cord extending from the common electric respective elements. Preferably, the prima cord extending thereto will range in length from a relatively short prima cord to the explosive being tested, to a relatively long cord to the flash bulb. Thus, when the firing device is actuated, the explosive being tested in the dark testing chamber will first be detonated and shortly thereafter in sequence the fuses l0 and H and the flash bulb will be detonated so that the detonation of the flash bulb will cause an image of the outline of the blast of the explosive being tested to be picked up by the camera lens.

During the taking of a photograph of an explosive charge, the fuses I0 and II detonate,

as hereinbefore described, and operate to partially cover the window 1 with a light resisting film of carbon a few microseconds before detonation of the flash bulb, as illustrated in Figure 4. At this point, the products of detonation and combustion from the fuses l0 and II will have reached a point just outside the angle of vision of the camera. Due to the previously described timing, the flash bulb will then be detonated and an image of the outline of the blast caused by the detonation of the explosive being photographed will be cast on the camera lens. Simultaneous with the completion of the aforesaid photograph, the products of detonation and combustion from the fuses l0 and II will meet adjacent a central portion of the window, as shown in Figure 5, and the window will be completely sealed against light. Thus, it will be readily understood that the camera lens is entirely shut oil! from any light resulting from any luminous post-detonation phenomena and the film is acfiring device to these through said opening,

4 cordingly protected against fogging or clouding. In other words, the immediate closing of the camera lens by the actuation of the shutter prevents fogging of the film due to light which may be associated with the detonation of the explosive being photographed.

What I claim is:

1. In combination with a camera for taking photographs of detonating explosives and the like in a testing chamber having an opening in a wall thereof, a transparent member covering said opening, means mounting said camera exteriorly of said chamber with its lens directed toward said opening, a frame member mounted on a wall of the chamber adjacent said transparent member, and fuse means arranged on said frame and adapted to be detonated to apply a light resisting coating to said transparent member after a photograph is exposed, said coating consisting of combustion products by the detonation of said fuze means.

2. In combination with a camera for taking photographs of detonating explosives and the like in a testing chamber having an opening in a wall thereof, a transparent window closing said opening, said camera being mounted exteriorly of said chamber, a frame member mounted on a Wall of the chamber adjacent said window, said frame member having a pair of substantially parallel explosive fuses arranged thereon for applying, on detonation, a light resisting coating of combustion products to said window after a photograph is exposed.

3. That method of shuttering a camera lens comprising detonating an explosive adjacent one Side of a transparent sheet extending over and across said lens to thereby deposit a light-resistant film of combustion products on said sheet.

4. That method of shuttering a camera lens comprising, exposing a photographic film in said camera through a transparent plate positioned over and across said lens, and immediately there after igniting an explosive positioned adjacent said plate to thereby directly deposit on said plate, a light-obstructing film of combustion products.

5. That method of shuttering a camera comprising, exposing a film in said camera through a transparent plate extending over and across the exposure opening of said camera, and immediately following said exposure, detonating a length of fuse cord positioned over and adjacent the surface of said plate remote from said camera, to thereby deposit a light-impeding film of combustion products over and across said surface.

6. In a shuttering device for a camera, an opaque wall having an opening, a sheet of transand means adapted to support a pair of parallel fuse cord sections adjacent and parallel to the other side of said sheet, said sections being symmetrically positioned upon opposite sides of the optical axis of said camera and adapted, when detonated, to cover said sheet with a light-obstructing film of combustion prodnets.

7. A shuttering device for a camera, comprising an opaque wall having an opening therein, a transparent plate secured over and closing said opening, a bracket mounted on said wall adjacent said opening, a pair of parallel primacord sections carried by said bracket in parallel re1ation with each other and said plate, said sections being symmetrically positioned on opposite sides of the central optical axis of said camera, there being a coating comprising a mixture of petroleum jelly and graphite on said sections.

8. The combination with a camera for taking photographs of detonating explosives and the like, of explosive shutter means, transparent protective means interposed between said shutter means and the camera, said shutter means being constructed and arranged to directly coat said protective means with an opaque coating of combustion products by and in response to detonation of said shutter means.

9. In combination with a camera for taking photographs of detonating explosives and the like and including a lens, of shutter means comprising a section of high explosive cord, a transparent protective member interposed between said shutter means and the camera lens, and means associated with said shutter means to automatically and directly apply to said member an opaque coating of combustion products resulting from ignition of said section of explosive cord.

10. In combination with a chamber for testing explosives and having an opening through the wall thereof, a transparent pane secured over said opening to close the same, a camera mounted externally of said chamber with its optical axis directed through said opening, and explosive shutter means mounted adjacent said pane and constructed and arranged to produce combustion products directly covering said pane with an opaque coating in response to detonation of said shutter means.

ARTHUR W. CAMPBELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,814,756 Levy July 14, 1931 1,917,245 Edwards et a1 July 11, 1933 1,936,595 Goddard Nov. 28, 1933 2,323,301 Anderson July 6, 1943 2,397,009 Hurley et a1 Mar. 19, 1946 2,399,476 Doyle et al Apr. 30, 1946 2,403,730 MacNeille July 9, 1946 

